Technical Field
The disclosure relates to a semiconductor device and a method for manufacturing the same, and in particular to a field effect transistor and a method for manufacturing the same.
Description of the Related Art
Junction field effect transistors (JFET) have been mostly used for analog switches and signal amplifiers, and especially for low noise amplifiers.
For a field effect transistor, an electric field near a carrier channel is mostly changed by controlling a signal (or bias of a gate), resulting in the change of the channel property and current property (between a source and a drain). Thus, the field effect transistor can be used for voltage controlled variable resistance, voltage controlled current source (VCCS), etc. The channel property and current property of the junction field effect transistor is changed by changing the width of the depletion region in the PN junction between the gate and the source/drain using the principle, whereby the function of the width of the deletion and the voltage is reversed.
Decreasing the gate voltage would increase the depletion region in the PN junction. If the gate voltage is low enough, all the channel is depleted and therefore no current flows from drain to source. The channel which is completely depleted is referred to as being pinched off. The gate voltage at which this effect occurs is referred to as the pinch-off voltage (VP). The present disclosure relates to a semiconductor device with low and adjustable the pinch-off voltage and a cost-effective method for manufacturing this semiconductor device.